Legume trees in a food forest

Discussion in 'Planting, growing, nurturing Plants' started by matto, May 4, 2011.

  1. matto

    matto Junior Member

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    Was just looking at the food forest trailer by Geoff Lawton.
    I am just wondering about peoples opinions about legume trees in the system. Im sure they are great as a nurse tree to provide shade and mulch, but I have heard that the nitrogen supporting bacteria only move millimetres and may not have a big effect on supplying nitrogen to the apex species.
    I would still look at using them anyway but just wondering what observations people have seen.
    Thanks for your insights
     
  2. garnede

    garnede Junior Member

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    The bacteria can reproduce and move along the legume's root system, but they don't supply the nitrogen to the other plants the legume does. As the legume roots die they release the nitrogen to the soil. Whatever plant is near will take advantage of it. Naturally fixed nitrogen can leach out of the soil just like chemical nitrogen can.
     
  3. bazman

    bazman Junior Member

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    If you use chop and drop with you legumes and use that as mulch around your fruit trees you will end up miles ahead. That's what I have always done in my food forest.
     
  4. matto

    matto Junior Member

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    Im totally with you there Bazman, Im just trying to workout what happens in the soil.
    I wonder if trees loose roots like grass does when the are pruned? Interplanting would then allow roots to crossover and fertilse once the legume root dies.
    Garnede, I was under the impression that it was the bacterial association on the roots and not the legume itself. This is why we need inoculants to make sure the bacteria is in the soil. Thats a good point about nitrogen leaching, thanks.
     
  5. insipidtoast

    insipidtoast Junior Member

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    Do roots grow up towards the surface of the soil? I always wonder how a surface dressing of mulch and compost manages to supply the tree with nitrogen. It seems if you kept adding organic material you would increase the depth of the topsoil, and thus increase the distance between the surface roots and the surface of the soil. What's keeping the plants from getting buried over time?
     
  6. matto

    matto Junior Member

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    Roots grow parallel to the surface as well as down off the tap root, although each specie is different. The nutrients from the mulch are leached down with water as well as by microbial action, and biota consuming the organic matter. Matter will be reduced like in your compost heap over time.

    I am seeing a necessity to ensure mycorrhizal fungi in the system to transport nitrogen, they exchange carbon for nutrients, most specifically phosphorus and zinc, but also exchange nitrogen and carbon between species. https://www.fromthesoilup.com.au/news/liquid-carbon-pathway-unrecognised
     
  7. garnede

    garnede Junior Member

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    My understanding is that the bacteria are needed for the legume to fix nitrogen, which it uses and stores. When it dies the stored nitrogen is released. I could be wrong though.
     
  8. bazman

    bazman Junior Member

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    I was told by a scientist friend years ago, that when nitrogen is produced in the legume nodules it is transported in seconds to the plants leafs, so the chop and drop idea puts this high nitrogen source where you lay out the chopped plant. The benefit I think with most legumes is they can recover quickly from coppicing and require no nitrogen fertilisers.
     
  9. Fernando Pessoa

    Fernando Pessoa Junior Member

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    You will find substantial nitrogen reserves in the leaves and seed pods of most of these species esp if they double as a fodder crop, nitrogen is fixed via the symbiosis of bacteria which must be introduced unless present already in the soil.The food forest video is an over simplification of this and if you think that you can support a commercially bred citrus tree with legume trees alone you will find yourself sadly lacking in yield.Food forest based on hardy low input requirement trees eg (inga edulis) other forest spiecies combined with supplementary feeding ie manures and composts do perform well and yield.Otherwise you are just growing bio mass,which is a yield but not the one you are after out of a food forest.
    Best wishes
    Fernando
     
  10. ptpermaculture

    ptpermaculture Junior Member

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    Ok, so here's my best shot at how nitrogen fixers function in a forest
    garden.

    1.) Firstly, there are different kinds of nitrogen fixers. Some fix nitrogen just because certain kinds of nitrogen fixing bacteria like hanging around their roots (some crop plants, eg. maize, wheat etc.). 2.) Others (the most common type, eg. Acacia spp.) fix nitrogen through a more intimate (symbiotic) association with a particular set of bacteria called Rhizobia (see here for a good description of Rhizobia). This second type has nodules on their roots in which the bacteria live, make nitrogen for themselves and share some with the plant. 3.) Another kind of nitrogen fixer has an association with a particular mychorhizal fungi which assists the plant in gathering nitrogen (eg. Casuarina spp.). 4.) Yet another ind have an association with ancient nitrogen fixers, cyanobacteria, such as Azolla and Macrozamia.

    In forest gardens, we are concerned with 2. and 3.

    As has been noted, there is limited movement of nitrogen from the roots themselves. Nitrogen is mostly used by plants (and the bacteria) to create protein. Nitrogen is an essential component for the manufacture of the amino acids which make up proteins. This means that nitrogen is locked up in leaves and (especially) seeds.

    The 'chop and drop' method can cause some flux of roots and a small amount of nitrogen. The principal addition of nitrogen, though, it provided by the decomposition of plant matter. That is, it has to be consumed again by bacteria and fungi. These bacteria and fungi then have to be consumed by soil predators to release the nitrogen which is othewise locked up in the bodies of the microbes.

    The great thing about this process is that these bacteria and fungi which are to be consumed usually hang around the root-zone of the plants we would like to have their nitrogen. When they are consumed, then, this nitrogen (predator poo) is delived right near the plants roots.

    That's my best go at it. I've love to hear whether people have another understanding. But the theme is:

    Nitrogen fixers - yes!

    Especially on the poor soils of Western Australia, where I am from, nitrogen fixers are essential. Native nitrogen fixers have proliferated here in great diversity to fill this ecological niche of fertility provision.

    Harry
    -----
    blog: https://perennialideas.ptpc.com.au
    permaculture: https://www.ptpc.com.au
    web design: https://myco.ptpc.com.au
     
  11. sweetpea

    sweetpea Junior Member

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    Definitely the nitrogen-fixing trees root prune when they are pruned, and those roots then break down releasing their nitrogen. Choosing trees that coppice well, chopping back the tree or bush hard, using all the parts. While the biomass and nitrogen may not go far, the idea is to plant under/near the tree, bring the crops to the tree. And deciduous nitrogen-fixing trees are more desirable as they will drop leaves in a mass that can be composted.

    I am worried, though, about invasive trees, especially in my area. It's a big deal where I am to not let non-native invasive trees and bushes/plants get a foothold, so I looked up native nitrogen fixers and am using those. They also do well in my climate with no help from me! Yay! They are also free when I can find them and pot them up, get them stabilized to be planted where I want them.

    I also live on the foggy coast, and having an upper canopy of shade over my vegetables is too shady, too cold, so I put the nitrogen fixing trees and shrubs on the north side of the garden (south side in the southern hemisphere) and that for me is on the uphill side of my garden as well, so bringing down the "harvest" of leaves and branches is easier, and they become a border of live composters. This works better to have them nearby rather than right smack in the middle of everything because I live in a Mediterranean climate, and the natives cannot have water in the summer once established, so growing lettuce and vegetables that need water would eventually kill my insectary/nitrogen fixers. So I try to plant annual flowers/companion plants in the beds with the vegetables, and those can stay and rot right in place at the end of the season.
     
  12. insipidtoast

    insipidtoast Junior Member

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    where do you live? I don't know of any native N-fixing trees that aren't riparian trees.
     
  13. matto

    matto Junior Member

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    Thanks for you great responses on this thread, you have cleared a few things up for me and made some good points.

    insipid, have a search for the Fabaceae family, otherwise known as the humble pea.
    alot of the acacia trees here are nitrogen fixing and are pioneer species. There might be a pattern there?
    Black Locust is a psuedo acacia, and fixes nitrogen
     
  14. ebunny

    ebunny Junior Member

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    What legume trees do people feel have been the most successful addition to their food forests in terms of soil conditioning?
     
  15. sweetpea

    sweetpea Junior Member

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    Insipid, not sure who your question is to, but "riparian" means next to a river, stream or pond. Is this the kind of tree you are looking for, one that can deal with a high water table?
     
  16. Pakanohida

    Pakanohida Junior Member

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    Alders and Honey Locust grow here. Legume trees aren't the only N fixing plant growing. Austrian peas, Crimson clover do as well in my food forest.



    With regards to a water table, -please- remember that all water tables go up and down based on local climatic factors all day long. Shade, evaporation, humus, and other factors increase and decrease the water level anywhere in a given day. Vicktor Schauberger has a wonderful dairy passage if you can find it ((1900's multi-generational ancient forest forester)) about a water spring shutting down thus removing water for many people because the source area had the trees, and brushes cut back. He and other mountain men of the time went up, replanted and made a shady building thing for the direct area over the spring. A short time later the spring came back despite the devastation around the spring area by humans.


    Schauberger is a very misunderstood and lil known scientist, loads of Forest & water ecology information.
     
  17. jonesalden

    jonesalden New Member

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    Hey...I want to grow Legume trees in a food forest. Please suggest me.
     
  18. tim@piginthemud

    [email protected] New Member

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    Hi All, I've just completed some permaculture diploma work that covers these topics in a number of downloadable journals. There are six in total that cover a range of topics all able to be leveraged in a food forest. Feel free to check them out on my website https://piginthemud.com/ Cheers, tim
     
  19. bazman

    bazman Junior Member

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    I use four here in sub-tropical Brisbane

    Pidgeon Pea, short lived spread randomly around my food forest. Often crop and drop.
    Popcorn cassia, short lived spread randomly around my food forest. Often crop and drop.
    Easter cassia, longer lived and planted right next to citrus trees, coppiced all year round.
    Ice-cream Bean, large long lived tree, coppiced with saw and chainsaw.

    I also use pinto peanut as a ground cover.
     
  20. ebunny

    ebunny Junior Member

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    Thanks Bazman. That's really helpful
     

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